Finland wants to become a member of NATO and will apply for membership of the defence alliance, Finnish President Sauli Niinistö and Prime Minister Sanna Marin said on Sunday in a step they greeted as historic.
Formally, the Finnish parliament must approve the plan but a majority is considered certain, as the country's ruling Social Democrats already endorsed the step on Saturday.
"A new era is beginning," Niinistö said.
Finland has been non-aligned for decades and the question of joining NATO was long considered unthinkable. However, Russia's attack on Ukraine lent the question new urgency and triggered intense political and public debate.
"When we look at Russia, we see a very different kind of Russia today than we saw just a few months ago. Everything has changed when Russia attacked Ukraine," Marin said. "I personally think that we cannot trust anymore that there will be a peaceful future."
"That's why we're making the decision to join NATO. It's an act of peace," she said, adding that Finland was prepared for possible responses from the neighbouring country.
"We have had wars with Russia, and we don't want that kind of future for ourselves, for our children, and this is why we're making these decisions today and in the upcoming weeks, so there will never again be a war," the Finnish premier said.
Niinistö and Marin jointly announced their support for Helsinki's accession on Thursday. Opinion polls also show that most people are in favour of the step.
Finland's announcement comes a day after Russian President Vladimir Putin warned Niinistö that joining NATO would be a mistake and that Russia posed no threat to Finland, according to a Kremlin statement.
Finland's departure from its traditional neutrality would cause the two countries' good neighbourly relations to deteriorate, Putin said.
Sweden, also traditionally a non-aligned country, also decided to apply for NATO membership.
Sweden to submit application
Sweden's ruling Social Democratic Party has announced its intention to submit an application, in a move that marks a major shift in their long-standing position on the defence alliance.
Swedish Prime Minister Magdalena Andersson's party came out in favour of her country joining NATO after a special meeting on Sunday, according to the party's website.
However, the Social Democrats have indicated they do not want nuclear weapons or permanent NATO bases on their territory.
The party's policy switch comes in response to Russia's invasion of Ukraine, which has triggered a rethink on NATO membership both in Sweden and neighbouring Finland.
Unlike their Nordic neighbours Denmark, Norway and Iceland, Sweden and Finland have never been members of NATO, despite closely cooperating with the alliance.